1. Field of the Invention
This invention relates to locking/unlocking mechanism, and more particularly, to a locking/unlocking mechanism for use on the extendable handle of a hand-trailable luggage case, which allows the user to easily unlock and draw out the extendable handle for use and also allows smooth operation of the locking/unlocking mechanism for prolong life of use.
2. Description of Related Art
A hand-trailable luggage case is widely used by travelers at airports to carry personal belongings, which is equipped with wheels and an extendable handle that allows the user to easily and effortlessly carry the luggage case by dragging it on the wheels along the ground. The extendable handle is normally retracted and locked in the luggage case and can be unlocked to be extended out for the user to drag the wheeled luggage case along the ground.
In conventional hand-trailable luggage cases, however, the locking/unlocking mechanism for the retractable handle is quite ineffective in operation, such as Wang, U.S. Pat. No. 5,526,908 discloses a Retractable Handle Assembly for a Suitcase, and Hsieh, U.S. Pat. No. 5,499,426 discloses a Retractable Handle Device for a Wheeled Suitcase which can cause the locking/unlocking mechanism inconvenient to use or cause wear to the same that would soon impair the locking/unlocking mechanism.
For simplifying the description, only taking Hsieh U.S. Pat. No. 5,499,426 for example to describe in detail with reference to FIGS. 1 and 2. FIGS. 1 and 2 are schematic side cross sectional views showing a retractable handle device at a locked and unlocked positions, respectively. As shown, the locking/unlocking mechanism of Hsieh's patent includes a push knob 71 and a pair of projecting members 82. Further, a pair of actuating members are formed beneath the push knob 71. Each of the projecting members 82 is formed with an inclined surface 823 which is functionally coupled to the actuating members of the push knob 71. Two compression spring 85 are provided between the two projecting members 82, which can urge the projecting members 82 outwards so as to lock the retractable handle in position when retracted. When the push knob 71 is pressed down by the user, it will cause the actuating members to move downwards and press on the inclined surfaces 823 of the projecting members 82, thus urging the projecting members 82 to come toward each other. When the projecting members 82 are withdrawn from the first engaging holes 900, the retractable handle will be unlocked that allows the user to freely extend it out for use.
One drawback to the foregoing locking/unlocking mechanism, however, is that the use of the knob 71 to urge against the projecting members 82 to unlock the retractable handle from the retracted position would not be reliable to use. In the event that the knob 71 is not pressing down directly on the center point but instead on a side point, the two actuating members of the knob 71 would not come into precise abutment on the respective inclined surfaces 823 of the projecting members 82 at the same time, causing the projecting members 82 to be unable to be withdrawn to unlock the retractable handle. Moreover, when the force applied by the user on the knob 71 is not evenly distributed over the surface of the knob, the locking/unlocking mechanism may not operate properly. The user may thus have difficulty in unlocking and extending out the handle. Moreover, the conventional locking/unlocking mechanism would be easily damaged due to wear.